Phase change ink printers conventionally receive marking material in a form known as an ink stick. The ink stick is a solid or semi-solid structure that may have any convenient shape (e.g., a pellet, block, brick, cube, or any other structure) for handling and loading into the printer. During use, ink sticks are inserted through an insertion opening of an ink loader for the printer and pushed or slid along a feed channel by a feed mechanism and/or gravity toward an ink melting assembly in the printer. The ink melting assembly melts the solid ink stick into a liquid that is delivered to one or more printheads for jetting onto an ink receiving surface.
Phase change ink imaging devices may be direct printing devices or indirect printing devices (also referred to as offset printers). In a direct printing device, the melted phase change ink may be emitted by the printhead(s) directly onto the surface of a recording medium. In offset printers, the melted phase change ink is emitted onto an imaging member that may be in the form of a rotating drum or a supported endless belt or band. A transfix roller is leveraged against the imaging member to form a transfer nip through which recording media are fed in timed registration with position of the ink on the imaging member. The pressure in the transfer nip causes the jetted phase change ink to transfer from the imaging member to the recording sheet.
In printers with an imaging member in the form of a rotatable drum, a release agent is often applied to the imaging member to form an intermediate transfer surface on the surface of the drum onto which the melted phase change ink is deposited by the printheads. The release agent is typically an oil or similar fluid material such as a silicone fluid that facilitates release of the melted phase change ink from the surface of the drum to the recording media in the transfer nip. Examples of systems or processes that utilize intermediate imaging members with release agents are shown in U.S. Pat. Nos. 5,372,852, 5,389,958, and 7,128,412.
To enable the use of release agent, phase change ink printers have been provided with release agent application systems. An example of a previously known release agent application system for a phase change ink printer is shown in FIG. 5. As depicted, the release agent application system includes a release agent applicator, in the example it is in the form of a roller, and a reservoir, such as a tub or trough, which holds a supply of release agent for the roller. The roller is formed of an absorbent material, such as extruded polyurethane foam, and is positioned with respect to the reservoir so as to be partially exposed to reclaimed release agent therein. Capillary forces cause the foam roller to absorb reclaimed release agent from the reservoir. The applicator contacts the surface of the imaging drum and applies release agent to the drum surface as the drum rotates. Once the release agent is deposited onto the imaging drum, the thickness of the release agent on the imaging drum is controlled by a metering blade so the amount of oil on the imaging member does not degrade the media sheet in the nip, the image being produced or interfere with ink transfer to the media. The metering blade is positioned to divert the excess oil away from the imaging drum and back into the release agent reservoir where it is reclaimed for reuse.
The reservoir is provided with a filter for removing debris, such as paper dust, dried ink, and the like, from the release agent prior to being reused by the applicator. The filter is positioned between the applicator and the release agent in the lower portion of the reservoir. A ground shield in the form of an L-shaped piece of metal is provided in the reservoir to position the filter and to act as a barrier for the excess release agent and contaminants it carries as it flows in a return path when diverted from the drum surface by the metering blade. In particular, the horizontal portion of the L-shape is positioned beneath the applicator and provides a spring like compliance force that presses the filter upward against the applicator surface and at the vertical portion of the L-shape applies a lateral grounding contact force against the applicator surface. The vertical portion of the support is positioned between the applicator and wall of the reservoir. The L-shaped support is spaced from the wall and bottom portion of the reservoir to shield the applicator from the reclaimed release agent and at the same time provide a flow path for the reclaimed release agent. The flow path directs the reclaimed release agent to the bottom portion of the reservoir where it is absorbed through the filter before reaching the applicator.
The compliance force applied by the L-shaped support varies based on bend angle tolerances, misalignment of the L-shaped support and roller with respect to each other as well as roller diameter variations as occurs in the normal manufacturing process. These system tolerance variations in turn cause variations in the force applied to the filter and roller such that the force may be increased to a degree that prevents the roller from rotating. At the opposite extreme of tolerance variation, a gap between the roller and filter or reduced area of contact may impede reclaim oil absorption into the roller.